- Hour 8: Windows Client for the Four Function Calculator
- Building a Proxy Class with WSDL.exe
- Summary
- Q&A
- Workshop
This chapter is from the book
This chapter is from the book
This chapter is from the book
Building a Proxy Class with WSDL.exe
An alternative to using the Visual Studio.NET Web Reference wizard to create your proxy classes is a DOS utility called WSDL.exe. WSDL.exe, although much more complicated to use than the Visual Studio tool, provides far greater control over the DLL that is created.
Another great benefit of the WSDL.exe is that it is built into the .NET framework. This means that developers creating ASP applications without the benefit of the Visual Studio.NET tool set can create proxy classes, compile them using a set of DOS compilers, and consume Web services in their applications.
Listing 8.2 shows the syntax for using the WSDL.exe. The switches, any of the commands proceeded by a /, are used to set various parameters of the utility. Switches in brackets, [], are optional, and if left off will either revert to some default or not be used at all.
Listing 8.2 The Syntax for the WSDL.exe
WSDL.exe [/language:] [/protocol:] [/namespace:]
[/username] [/password] [/domain]
[/out:] <url or path>
Table 8.1 shows the various switches used by the WSDL.exe application. The switches pertaining to working with a proxy server and to switching base URLs have been left out. If you need to accomplish one of these tasks, you can get help by simply typing
Wsdl /?
Table 8.1 WSDL.exe's Switches
|
Command |
Short |
Description |
|
url or path |
|
The URL, or path name if the file has been stored locally, to an SDL, XSD, or discomap file. |
|
/nologo |
|
Turns off the banner. |
|
/language |
/l |
Chooses the language that the proxy will be generated in. VB, JS, and CS are all valid. |
|
/server |
|
Triggers the generation of an abstract class for the XML Web service. |
|
/namespace |
/n |
Determines the namespace of the generated proxy class. |
|
/out |
/o |
The path and file name of the generated proxy class. |
|
/protocol |
|
Can set the proxy to work with SOAP, httpGet, or httpPost protocols. |
|
/username |
/u |
Username for authenticating to a server. |
|
/password |
/p |
Password for authenticating to a server. |
|
/domain |
/ |
Domain for authenticating to a server. |
|
/proxy |
|
Url of the proxy server being used for http requests. |
The out switch and path or url are the two settings that you will need to concern yourself with the most when creating proxies. In order to create a proxy, the out switch needs to be set to a valid file name—for example, SomeName.VB, in the case of a Visual Basic proxy. The path needs to be set to the URL or local file path of the Web Service's WSDL file.
NOTE
It is a good idea to use a tool such as Internet Explorer to confirm the path to a Web Service's WSDL file before you enter it into the WSDL.exe's path switch. Errors will result if the path switch has the utility pointing to an incorrect URL.
Creating the Four Function Calculator's Proxy with WSDL.exe
Open a DOS Window and, at the C prompt, type in the command in Listing 8.3. This will create a proxy class called FourFunctionCalc.cs and place it in a directory called book on your C drive. Feel free to modify the directory that you save the proxy class to. The command also gives the proxy a namespace of FourCalc.
Listing 8.3 Using WSDL.exe to Create a Proxy Class for the Four-Function Calculator
C:\>WSDL.exe /language:CS /namespace:FourCalc /out:c:\Captures\FourCalc.cs http:\\localhost/FourFunctionCalc/Service1.asmx?sdl
NOTE
You can use the optional language tag to create the proxy class in Visual Basic if you wish to examine the code and are more comfortable with Visual Basic. There is almost never a reason to alter this class yourself. For the purposes of this example, you can let the proxy be created using the default language, C#.
Figure 8.8 shows how the DOS window should appear if you have successfully created your proxy class.
){kind=link}
Figure 8.8 Creating the Four Function Calculators Proxy Code
Now, you can compile the class into a usable dll. This can be done by either opening the class in Visual Studios, or by using one of the command line compilers that ships with the .NET framework. Those compilers, reachable through a DOS prompt, are csc, to compile C# code, and vbc, for compiling Visual Basic code. With these compilers, it is possible, though not at all advisable, to write complete programs in a Word Processor, even one as simple as Notepad, and compile them.
Listing 8.4 shows the command syntax for compiling your C# class.
Listing 8.4 Compiling the Proxy Class
1: C:\>csc /t:library /r:System.Web.Services.dll 2: /out:c:\Book\FourCalc.dll c:\Captures\FourCalc.CS
NOTE
The command in Listing 8.4 should be entered in as one continuous line with space appearing before each / switch.
The /t or target switch is set to library, which lets the compiler know that you are trying to create a DLL. The /r or reference switch tells the compiler to include a reference to System.Web.Services.dll.
The final switch of the command is the /out switch, which sets the name and path of the DLL you wish to create. In this case, you are creating a DLL called FourCalc to be placed in the directory c:\Book. You may feel free to change the directory to whatever you like.
The last portion of the command is the path to the proxy class that was created by the WSDL.exe, c:\Captures\FourCalc.cs or whatever path you saved the file to.
To obtain help on the csc, C# compiler, type in the following command at a DOS prompt:
csc /?
In order to obtain help on the Visual Basic command line compiler, vbc, type the following in at a DOS prompt:
vbc /?
These compilers include the ability to generate bug reports, link additional resources, set precompiler directives, and much more.
Adding a Reference to a Proxy DLL
Once you have created and compiled the FourCalc.dll, you can begin using it in your client applications. Create a new Windows application called FourCalcClient to act as the client to your new proxy.
Inside your new project, create a form identical to the one you created in the CalcClient application (see Figure 8.1 for the form's layout).
){kind=link}
You can now add a reference to your FourCalc proxy. This time, because the proxy is already created and local, you will add the reference the way you would any other DLL. Choose Add Reference from the Project menu to bring up the Add Reference dialog. From there, choose Browse and navigate to your FourFunc.dll. Figure 8.9 shows the Select Component dialog for finding components.
){kind=link}
Figure 8.9 Adding a reference to the four function calculator's proxy.
Now that you have found and selected your component, add a reference to the System.Web.Services.dll. You should see both DLLs at the bottom of the Add Reference screen, in the Selected Components window (see Figure 8.10).
){kind=link}
Figure 8.10 Adding all the references to the four function calculator.
Using the WSDL.exe-Generated Proxy Class
After you have added your references, using the XML Web service proxy is just like using the proxy generated by Visual Studio .NET, except that you have control over the location of the DLL and can reuse the DLL in additional projects without having to go through the trouble of using the Add Web Reference dialog again.
To create an instance of the FourCalc.dll's Service1 object, add the following line to the general declarations section of your FourCalcClient's Form1:
Dim oCalc As New FourCalc.Service1()
After creating the oCalc object, you can add code to the button events of Form1. The code for these events is identical to that of the CalcClient application, shown in Listing 8.1.
You can now run the application and verify that both versions of the four-function calculator's clients behave in exactly the same manner.